In recent years, in a field of mobile computing in particular, a demand for a memory which is formed compact, can be easily carried and has a large data capacity has been increased. A planar optical waveguide type optical memory using a planar optical waveguide as a data area can be increased in capacity by superimposing planar optical waveguides, and appears promising as a storage medium in future. Further, an optical memory reproduction apparatus which reproduces data from such a planar optical waveguide type optical memory has been also studied in many ways.
FIG. 1 is a view showing a configuration and a utilization mode of a conventional optical memory reproduction apparatus 1A.
The optical memory reproduction apparatus 1A is an apparatus which reproduces data from an optical memory medium 2 formed by alternately superimposing a core 21 and a clad 22 constituting a planar optical waveguide.
In data reproduction by the optical memory reproduction apparatus 1A, a light source 11 first emits a collimated laser light 1 toward an end surface 200 of the optical memory medium 2. Further, a condenser lens 12 condenses a part of the laser light 111 into a dot-like or a circular pattern, thereby generating a read light 103 which travels in a direction of the optical memory medium 2.
When the read light 103 reaches the end surface 200 of the optical memory medium 2, a part of this light enters the core 21. A data image 203 obtained by two-dimensionally recording data by using a scattering factor is written in an optical coupling area 2103 where the core 21 is coupled with the read light 103. The scattering factor expressing the data image 203 is formed as, e.g., irregularities on an interface between the core 21 and the clad 22 or a change in refraction index of the core 21 in the core 21.
When the read light 103 is coupled in the optical coupling area 2103, the read light 103 scatters and interferes by the data image 203, and exits as a data reproduction light 1031 to the outside of the optical memory medium 2 from the interface between the core and the clad or the inside of the core where the scattering factor is formed through the clad.
Then, the data reproduction light 1031 is imaged by an imaging element 133, and a data reproducing section 14 reproduces data based on an obtained reproduction image.
In order to reproduce data stored in the optical memory medium without an error by using the optical memory reproduction apparatus 1A, a read light must be caused to accurately enter a target core.
It is to be noted that the detail of positioning of the read light is described in Japanese Patent Application Laid-open No. 2003-51122.
However, the content of Japanese Patent Application Laid-open No. 2003-51122 is an example using a zonal read light which does not spread in the core, and it cannot be applied to positioning of a read light which travels while spreading in a core, e.g., a read light which is condensed toward a focal point and spreads from the focal point. As a result, when a spreading read light is used, positioning of this light cannot be carried out, and realization of such an optical memory reproduction apparatus is obstructed.